Often, permanent magnet motors used in automotive applications require the use of more than one speed, usually a lower speed for general-purpose operation and a maximum speed for worst-case operation. Multiple speed operation of the cooling system module provides a more optimized engine temperature and operation, which consequently contributes to improved fuel economy.
For PMDC BM historically lower speeds (multiple speed operation) have been achieved by the following methods:                Adding a resistor in series with the motor        Switching out brushes        Dual armature winding with dual commutator        Adding an additional 3rd brush (short out coils)        External or internal electronic control comprised of but not limited to        SSR, (Solid State Relays)        Linear control        PWM, (Pulse Width Modulation)        
The embodiment relates to a motor configuration with dual-armature windings and dual commutator configuration for a two-speed application. The DC motors having a dual-armature winding and two commutators are well known in the art. The following U.S. patents describe the art of dual-armature winding and dual commutators well: U.S. Pat. Nos. 5,925,999 and 4,910,790, and are hereby incorporated into the present specification by reference.
The current two speed motor configuration with dual-armature winding and two commutators is not cost competitive on the market compared to a two speed solution such as adding a resistor in series with the motor. However, the dual-armature winding with the two-commutator configuration is a more elegant and efficient method for two-speed application than the series resistor solution. Furthermore, from system and energy conservation point of view, the dual-armature winding (with two commutators) motor configuration is more effective than the motor with a series resistor; considering the fact that during the second speed (low speed) operation there is approximately a 20 to 25% current saving with a motor having the dual-armature winding (with two commutators) compared to a motor (of same type and size) with series resistor for low speed.
A conventional brush card assembly is shown in FIGS. 1 and 2. These two figures clearly illustrate the ingenuity and complexity of that configuration. FIG. 1 shows a Low Speed (LS) side of the brush card assembly, generally indicated at 10 and FIG. 2 shows a High Speed (HS) side of the same brush card assembly 10. There are total of eight brushes 12 and eight brush springs 14 and eight brush tubes 16 (4 sets for each side, LS and HS). Furthermore, there is a complex over molded terminal bar frame 18 which conveys power to the brushes 12 and interconnects the dual-armature windings (not shown).
Accordingly, there is a need to provide a brush card assembly for two-speed motor assembly that is more cost effective (lesser components) and of simpler configuration than conventional brush card assemblies, without compromising the functionality and integrity of the brush card assembly and motor assembly.